Quick-set film-forming compositions

ABSTRACT

The present invention relates to a quick set composition and a method for preparing the composition. The composition comprises an aqueous sol of a polymer having a backbone that contains pendant cationic groups and pendant acid groups. The sol is prepared by forming a solution of a polymer that contains pendant cationic groups and pendant acid groups in an aqueous-based solvent that contains water and a suitable organic solvent and removing a sufficient amount of the organic solvent from the solution to form a composition characterized by being reversibly dissolvable and reconstitutable by addition and removal of a suitable organic solvent. The composition of the present invention provides quick-set films that can be prepared in the absence additional surface active agents and with a substantial absence of organic solvents.

CROSS-REFERENCE TO RELATED APPLICATION

This invention is a divisional of application U.S. Ser. No. 09/151,933,filed Sep. 11, 1998, now U.S. Pat. No. 6,191,211.

BACKGROUND OF THE INVENTION

The present invention relates to a water-dispersible polymericcomposition that can be used to prepare quick-set films or coatings.

Coatings provide protective barriers for a variety of things includingfloors, automobiles, exteriors and interiors of houses, and human skin.Protective coatings for floors, for example, have been known since themid 1950s. Many of the early coating materials were applied usingpetroleum- or naphthene-based solvents and as such were undesirable dueto the toxicity and flammability of these solvents.

Water-based synthetic emulsion compositions, such as styrene resinemulsions, styrene-acrylate copolymer resin emulsions, and acrylateemulsions, developed in the early 1960s, gradually replaced organicsolvent-based compositions. Although these water-based compositions areless toxic and more environmentally friendly than organic solvent-basedcompositions, the water-based compositions tend to be slow to set anddifficult to remove in an application where removability is desired.Removal of coatings may be desirable because even the most durablecoatings tend to deteriorate due to soiling or wear and tear. In otherapplications, such as protective care products for the skin, theadvantages of water-based removable coatings are obvious.

Removable, water-based coatings are known. For example, polymers thatcontain ammonium carboxylate functionality are water compatible, butbecome incompatible through the loss of solvent and ammonia.

Coatings made by the above-illustrated process can be subsequentlyremoved by contact with an aqueous alkaline liquid, which converts theacid back into the compatible salt.

For example, in U.S. Pat. No. 4,622,360, Gomi et al. discloses aremovable water-borne polyurethane resin containing carboxyl groups.Coating compositions can be prepared by adding a polyvalentcomplex-forming metal to the water-borne resin. The polyvalent metalforms a stable water-dispersible complex with an amine or ammonia in theaqueous solution. When the dispersion is applied to a floor surface,noxious volatile materials evaporate to allow the polyvalent metal ionsto initiate a crosslinking of two or more carboxyl groups, therebyforming a hardened, water-incompatible coating. This hardened coatingcan be removed, but only with a harsh alkaline solution containingligands such as ethylene diamine tetraacetic acid.

The ammonium carboxylate coating suffers from several disadvantages: 1)the formulations are malodorous and irritating to the eyes and skin; 2)long set times are required to attain acceptable physical properties ofthe coating; and 3) the removal or stripping process requires the use ofhazardous alkaline liquids.

In view of the deficiencies of the known art, it would be desirable tohave a composition that provides a quick-set film or coating that can beremoved without the use of harsh chemicals in applications where suchremoval is desirable. It would further be desirable to render such acoating resistant to common organic solvents in applications wheregeneral solvent resistance is desired.

It would further be useful to have a hypoallergenic, non-toxic,water-based composition that provides a coating that gives long-lastingprotection to the skin against sun, dryness, and harsh chemicals.

SUMMARY OF THE INVENTION

The present invention is a composition comprising an aqueous-based solof a polymer having a backbone that contains pendant cationic groups andpendant acid groups, which sol is prepared by the steps of:

a) forming a solution of a polymer that contains pendant cationic groupsand pendant acid groups in an aqueous-based solvent for the polymer,which solvent contains a first organic solvent; and

b) removing a sufficient amount of the first organic solvent from thesolution to form a composition characterized by being reversiblydissolvable and reconstitutable by addition and removal of a secondorganic solvent.

In a second aspect, the present invention is a method of coating asubstrate comprising the step of applying to a surface of the substratea composition containing a water-compatible coalescing agent and anaqueous-based sol of a polymer having a backbone that contains pendantcationic groups and pendant acid groups, wherein the sol is prepared bythe steps that comprise:

a) forming an aqueous-based solution of the polymer, which solutioncontains an organic solvent;

b) removing a sufficient amount of the organic solvent from the solutionto form a composition having a minimum solids content such that theviscosity of the sol is less than half the viscosity of the solutionhaving the same solids content;

wherein the coalescing agent is an organic liquid having a boiling pointgreater than 100° C.

In a third aspect the present invention is a composition comprising anaqueous-based sol of a polymer having a backbone that contains pendantcationic groups and pendant acid groups wherein the sol is furthercharacterized by being reversibly dissolvable and reconstitutable byaddition and removal of an organic solvent for the sol.

The composition of the present invention provides quick-set films thatcan be prepared in the absence of additional surface active agents andwith a substantial absence of organic solvents. The sol affords a higherconcentration of solids at considerably lower viscosities than acorresponding solution.

DETAILED DESCRIPTION OF THE INVENTION

The composition of the present invention comprises an aqueous-based solof a polymer having a backbone that contains pendant cationic groups andpendant acid groups.

As used herein, the terms “aqueous-based sol” or “sol” refer to asuspension of the polymer in a water-containing medium. The medium mustinclude water, and may include a suitable organic solvent. The sol ischaracterized by being reversibly dissolvable and reconstitutable (thatis, returned to the sol state) by addition and subsequent removal of asuitable organic solvent, which may be the same as or different from theorganic solvent that may be present in the sol. It is also possible toremove all of the aqueous-based solvent from the sol to form a solid,and then reconstitute the sol by dissolving the solid in a suitableaqueous-based solvent, then removing a sufficient amount of the organicsolvent (and optionally adding sufficient water) to reconstitute thesol. The suspended particles preferably have an average particle size(as measured by a Coulter Model N4MD Sub-Micron Particle Analyzer) ofnot less than 10 nm, and more preferably not less than about 20 nm, andpreferably not more than about 500 nm, more preferably not more thanabout 300 nm, and most preferably not more than 200 nm.

The dissolved polymer is differentiated from the sol by the differencesin the viscosities of the two compositions at a given minimum polymerconcentration and the amount of organic solvent needed to form asolution. Specifically, the viscosity of the sol is preferably less thanhalf, more preferably less than one-third, and most preferably less thanone-tenth the viscosity of the dissolved polymer at a polymerconcentration of not less than about 5 weight, more preferably not lessthan about 10 percent, based on the weight of the solution or sol.Furthermore, the minimum amount of organic solvent required to form asolution is greater than the maximum amount of organic solvent requiredby a sol. Specifically, the minimum amount of organic solvent requiredto form a solution is typically greater than 20 weight percent based onthe weight of the polymer and the aqueous-based solvent. On the otherhand, the maximum amount of the organic solvent required by a sol istypically less than 20, more preferably less than 10, and mostpreferably less than 6 weight based on the weight of the polymer and thesol.

The polymer is characterized by containing pendant cationic groups andpendant acid groups. Generally, these pendant groups can be formed fromthe polymerization of a polymerizable cationic monomer, preferably astrong cationic monomer, and a polymerizable acid monomer, which may bea strong acid or a weak acid monomer. As used herein, the term “strongcationic monomer” refers to a monomer that contains ethylenicunsaturation and a cationic group having a charge that is independent ofpH. The term “polymerizable acid monomer” refers to a monomer thatcontains ethylenic unsaturation and an acid group.

In addition to containing pendant cationic and acid groups, the polymerpreferably includes structural units that can be formed from thepolymerization of a polymerizable non-interfering monomer. The term“polymerizable non-interfering monomer” is used herein to refer to anuncharged monomer that does not adversely affect the formation andproperties of a film or a coating prepared from the sol. The term“structural units formed from the polymerization of a polymerizable . .. monomer” is illustrated by the following example:

Polymerizable acid monomers that are suitable for the preparation of thedispersion used to prepare the quick-set coating include ethylenicallyunsaturated compounds having carboxylic acid, phenolic, thiophenolic,phosphinyl, sulfonic acid, sulfinic acid, phosphonic, or sulfonamidefunctionality, or a combination thereof. Preferred polymerizable acidmonomers include acrylic acid, methacrylic acid, itaconic acid,β-carboxyethyl acrylate (usually as a mixture of acrylic acidoligomers), vinylbenzoic acid, vinylchlorophenol, vinylbromophenol,vinylthiophenol, 2-propenoic acid: 2-methyl-, (hydroxyphosphinyl) methylester, vinylphosphonic acid, 2-acrylamido-2-methyl-1-propane sulfonicacid, and 2-sulfoethyl-methacrylate. Acrylic acid, methacrylic acid,2-acrylamido-2-methyl-1-propane sulfonic acid, and vinylphosphonic acidare more preferred acid monomers, and acrylic acid, and methacrylic acidare most preferred.

The polymerizable cationic monomer is associated with a counterion, forexample, halide such as chloride or bromide, nitrate, phosphate,carbonate, bicarbonate, acrylate, methacryate, or sulfate. Suitablepolymerizable strong cationic monomers include salts of ethylenicallyunsaturated compounds having quaternary ammonium, sulfonium, cyclicsulfonium, and phosphonium functionality. Examples of suitable monomershaving quaternary ammonium functionality include ethylenicallyunsaturated trialkylammonium salts such as vinylbenzyltri-C₁-C₄-alkylammonium chloride or bromide; trialkylammoniumalkylacrylates or methacrylates such as2-[(methacryloyloxy)ethyl]trimethylammonium chloride and N,N-diethyl-N-methyl-2-[(1-oxo-2-propenyl)oxy]ethanaminium methyl sulfate(Chem. Abstracts Reg. No. 45076-54-8); and trialkylammoniumalkylacrylamides such asN,N,N-trimethyl-3-[(2-methyl-1-oxo-2-propenyl)amino]-1-propanaminiumchloride (Chem. Abstracts Reg. No. 51441-64-6) and N,N-dimethyl-N-[3-[(2-methyl-1-oxo-2-propenyl)amino]propyl]-benzenemethaminiumchloride (Chem. Abstracts Reg. No. 122988-32-3). A preferredpolymerizable quaternary ammonium salt is2-[(methacryloyloxy)ethyl]trimethylammonium chloride.

Other examples of suitable cationic monomers include amine salts such assalts of substituted or unsubstituted aminoalkyl methacrylates andaminoalkyl acrylates. Aminoethyl methacrylate hydrochloride is anexample of a suitable amine salt.

Examples of polymerizable unsaturated sulfonium salts includedialkylsulfonium salts such as[4-ethoxy-3-(ethoxycarbonyl)-2-methylene-4-oxobutyl]dimethylsulfoniumbromide (Chem. Abstracts Reg. No. 63810-34-4); and vinylbenzyldialkylsulfonium salts such as vinylbenzyl dimethylsulfonium chloride.Examples of polymerizable cyclic sulfonium salts include1-[4-[(ethenylphenyl)methoxy]phenyl]tetrahydro-2H-thiopyranium chloride(Chem. Abstracts Reg. No. 93926-67-1); and vinylbenzyltetrahydrothio-phenonium chloride, which can be prepared by the reactionof vinylbenzyl chloride with tetrahydrothiophene.

Examples of polymerizable phosphonium salts include2-methacryloxyethyltri-C₁-C₂₀-alkyl-, aralkyl-, or aryl-phosphoniumsalts such as 2-methacryloxyethyltri-n-octadecyl-phosphonium halide(Chem. Abstracts Reg. No. 166740-88-1); tri-C₁-C₁₈-alkyl-, aralkyl-, oraryl-vinylbenzylphosphonium salts such astrioctyl-3-vinylbenzylphosphonium chloride,trioctyl-4-vinylbenzylphosphonium chloride (Chem. Abstracts Reg. No.15138-12-4), tributyl-3-vinylbenzylphosphonium chloride,tributyl-4-vinylbenzylphosphonium chloride (Chem. Abstracts Reg. No.149186-03-8), triphenyl-3-vinylbenzylphosphonium chloride, andtriphenyl-4-vinylbenzylphosphonium chloride (Chem. Abstracts Reg. No.145425-78-1); C₃-C₁₈-alkenyltrialkyl-, aralkyl-, or aryl-phosphoniumsalts such as 7-octenyltriphenyl-phosphonium bromide (Chem. AbstractsReg. No. 82667-45-6); andtris(hydroxymethyl)-(1-hydroxy-2-propenyl)phosphonium salts (Chem.Abstracts Reg. No. 73082-48-1).

The polymer that contains pendant cationic groups and acid groups canalso be prepared from a monomer that contains both an acid group and astrong cationic group. Examples of such monomers includeN-(4-carboxy)benzyl-N,N-dimethyl-2-[(2-methyl-1-oxo-2-propenyl)-oxy]ethanaminium chloride andN-(3-sulfopropyl)-N-methacroyloxyethyl-N,N-dimethyl ammonium betaine.

It is also possible to prepare a polymer that contains cationic groupsand acid groups by adding cationic functionality to an already preparedpolymer. For example, a polymerizable monomer having a weak acid groupcan be copolymerized with a polymerizable non-interfering monomercontaining an electrophilic group, such as vinylbenzyl halide orglycidyl methacrylate, to form a polymer having a weak acid group and anelectrophilic group. This polymer can then be post-reacted with anucleophile such as a tertiary amine, pyridine, a dialkyl sulfide, or acyclic sulfide, which can displace the halide group or open the oxiranering and form an onium salt. An example of the formation of abenzylonium salt is illustrated as follows:

where A is a pendant weak acid group; Ar is an aromatic group,preferably a phenyl group; L is a leaving group, preferably a halidegroup, more preferably a chloride group; and Nu is the nucleophile.

In another example of adding cationic functionality to an alreadyprepared polymer, a polymer backbone that contains pendant acid groupsand a tertiary amine or a sulfide can be post-reacted with an alkylatingreagent such as an alkyl halide to form a polymer that contains acidgroups and strong cationic groups:

where RL is an alkylating reagent.

Examples of non-interfering polymerizable monomers include acrylatessuch as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexylacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, glycidylacrylate, and allyl acrylate; methacrylates such as methyl methacrylate,ethyl methacrylate, butyl methacrylate, allyl methacrylate, glycidylmethacrylate, 2-hydroxyethyl methacrylate, polypropylene glycolmonomethacrylate, and 2-hydroxypropyl methacrylate; alkenyl aromatichydrocarbons such as 4-methacryloxy-2-hydroxy-benzophenone,2-(2′-hydroxy-5-methacrylyloxyethylphenyl)-2H-benzotriazole; and analkenyl aromatic hydrocarbon, or C₁-C₄ alkyl- or alkenyl-substitutedstyrenes, preferably styrene, α-methylstyrene, vinyltoluene, andvinylbenzyl chloride. Other examples of non-interfering speciesC₃-C₁₈-perfluoroalkyl methacrylates such as 2-(perfluorooctyl)ethylmethacrylate; C₃-C₁₈-perfluoroalkyl acrylates such as2-[ethyl[(heptadecafluorooctyl)-sulfonyl]amino]ethyl 2-propenoate; andC₃-C₁₈-perfluoroalkyl vinylbenzenes. (See U.S. Pat. No. 4,929,666,column 4, lines 54 to 68, and column 5, lines 1 to 30.)

Preferably, the mole ratio of pendant acid groups to pendant cationicgroups is not less than about 0.1, more preferably not less than about0.2, and most preferably not less than about 0.5; and preferably notmore than about 10, more preferably not more than about 5, and mostpreferably not more than about 2.

The preferred mole ratio of the structural units formed from thepolymerization of the polymerizable non-interfering monomer to the sumof the structural units formed from the polymerization of thepolymerizable acid monomer and the polymerizable cationic monomer (or,alternatively, the sum of the pendant acid groups and the cationicgroups) is preferably not less than 70:30, more preferably not less than80:20, and most preferably not less than 85:15; and preferably notgreater than 99:1, and more preferably not greater than 98:2, and mostpreferably not greater than 95:5.

Typically the polymer has a number average molecular weight in the rangeof from about 1000 to about 200,000 Daltons, preferably from about 8000to about 50,000 Daltons.

The composition of the present invention can be prepared by the steps ofpolymerizing the acid monomer, the cationic monomer, and preferably thenon-interfering monomer in the presence of water and a sufficient amountof an organic solvent for the polymer to form a solution of thesubsequently formed polymer. An organic solvent useful for forming anaqueous-based solution of the polymer is one that a) forms a singlephase with water in the concentrations used; b) is substantiallycompletely removable from the solution, preferably by rotaryevaporation, without completely removing the water; and c) is, in somecombination with water, a solvent for the polymer. More preferably, theorganic solvent has a boiling point of less than 100° C. It is to beunderstood that the suitable solvent may be a combination of organicsolvents.

Examples of organic solvents useful for the polymerization includeethers, alcohols, esters, nitrites, and ketones, and combinationsthereof. Examples of more preferred organic solvents include methanol,ethanol, 1-propanol, 2-propanol, 2-methyl-2-propanol,2-methyl-1-propanol, 1-butanol, and propylene glycol methyl ether, ethylacetate, acetonitrile, or combinations thereof. Preferably, the amountof organic solvent used in the polymerization step is not less than 20,more preferably not less than 30, and most preferably not less than 40weight percent based on the weight of water and the solvent; andpreferably not greater than 80, more preferably not greater than 70, andmost preferably not greater than 60 weight percent based on the weightof polymer and aqueous-based solvent. The polymerization reactiongenerally is carried out at elevated temperatures, typically betweenabout 50° C. and about 100° C., and in the presence of a polymerizationinitiator.

Upon completion of polymerization, a sufficient amount of the organicsolvent is removed to form the sol. Solvent removal can be accomplishedin a number of different ways. In one method, the aqueous-based solutioncontaining the polymer is preferably cooled, and the solids contentdetermined so that a sol with a desired solids content can readily beprepared. The solution may optionally be diluted with water and anorganic solvent to maintain a solution and to achieve the final desiredsol concentration upon subsequent removal of the organic solvent. Theorganic solvent is characterized by being completely removable, oralmost completely removable, without completely removing the water; theconcomitant addition of water and removal of organic solvent ispreferred. A sufficient amount of the organic solvent can then beremoved, preferably in vacuo, to form a sol having a solids content ofpreferably not less than 5 percent, more preferably not less than 10percent, and most preferably not less than 20 percent based on theweight of water and the polymer. Both the organic solvent that was usedalong with water to form the polymer solution and the solvent that wasadded after completion of polymerization (which may or may not be thesame solvent) can be removed. Preferably the total amount of organicsolvent removed in the solvent removal step is at least 90 percent, morepreferably at least 95 percent. Thus, the sol is preferablysubstantially free of organic solvent.

In another method of preparing the sol, the organic solvent may beremoved by steam stripping. In this technique, it may be desirable toadd additional water during stripping to adjust the solids content.

The aqueous-based sol of the present invention can generally bedistinguished from an emulsion polymerized aqueous dispersion (latex) ofa polymer having pendant cationic groups and pendant acid groups in anumber of ways. First, unlike the latex, the polymer particles dispersedin the sol can be dissolved in a suitable organic solvent (or a suitableaqueous-based solvent such as the solvent used to form the sol), andreconstituted, or concentrated to a gel and diluted to re-form the sol,or concentrated to a solid then redissolved to form a solution, whichcan then be reconstituted to form the sol. The suitable organic solventcan be the same as or different from the organic solvent that is usedwith water to dissolve the polymer.

Second, the preferred sol of the present invention is even furtherdistinguished from the corresponding latex in that the sol is preferablyprepared in the substantial absence of any additional surface activeagent (that is, not more than 0.5 percent, preferably not more than 0.1percent of an added surfactant) while the latex is preferably preparedin the presence of greater than 0.5 weight percent levels of anadditional surface active agent. The term “additional surface activeagent” refers to surface active agents other than the pendant cationicand acid groups of the polymer, or the polymerizable cationic and acidmonomers used to prepare the polymer.

Third, the preferred number average molecular weight of the sol is lessthan 50,000 Daltons while the latex tends to have a molecular weightthat exceeds 100,000 Daltons.

One notable advantage of the sol as compared to the solution is that ahigher percent solids composition can be prepared without detrimentaleffects on the the viscosity. A higher solids loading is beneficialbecause these more concentrated sols exhibit more desirable physicalproperties. Whereas solutions having a solids content of greater than 20percent are impracticle because of their high viscosity, the preferredsol flows easily at a solids content of 20 percent and even higher.Moreover, the sol is preferably substantially absent of organicsolvents, except perhaps for a minimum amount that may be added as acoalescing agent to the final coating formulation.

A coalescing agent may be advantageously combined with the sol,particularly if it is necessary to reduce the minimum film-formingtemperature. The coalescing agent is an organic solvent, or combinationof organic solvents, which function to give a clear adherent film. Thecoalescing agent is typically a high boiling organic liquid preferablyhaving a boiling point that is greater than 100° C. The coalescing agentis also water compatible, that is to say, water-soluble at theconcentrations used, or, in combination with another coalescing agent,water-soluble at the concentrations used. When the coalescing agent isused, the amount added is preferably not more than 20 weight percent,more preferably not more than 10 weight percent, and most preferably notmore than 6 weight percent, based on the weight of the sol and thecoalescing agent. Preferred coalescing agents include glycol ethers,dibasic esters, nitrites, carbonates, sulfoxides, amides, pyrrolidones,and combinations thereof. Examples of more preferred coalescing agentsinclude benzonitrile, dimethyl succinate, dimethyl glutarate, dimethyladipate, dipropylene glycol dimethyl ether, propylene glycol n-butylether, dipropylene glycol n-butyl ether, dipropylene glycol n-propylether, propylene glycol methyl ether acetate, dipropylene glycoldimethyl ether, dimethyl formamide, dimethylsulfoxide, propylenecarbonate, N-methyl-2-pyrrolidone, ethylene glycol phenyl ether,diethylene glycol methyl ether, diethylene glycol n-butyl ether,ethylene glycol n-butyl ether, propylene glycol n-propyl ether,propylene glycol phenyl ether, dipropylene glycol methyl ether acetate,tripropylene glycol methyl ether, dipropylene glycol methyl ether andpropylene carbonate, and combinations thereof.

The coalescing agent may be added at any time during the process forpreparing the sol, including during the polymerization step. If theagent is added during the polymerization step, a sufficient amount ofthe agent is advantageously removed to both a) form the sol; and b)maintain coalescing capabilities.

The coatings described thus far are resistant to water, but can easilybe removed with a mixture of solvents or a combination of acid andsolvent, such as a combination of water and an organic solvent, morepreferably water and 1-propanol. These coatings can be renderedsubstantially permanent, that is, resistant to removal by organicsolvents as well as aqueous-based acids or bases, in at least threeways. First, an effective amount of a crosslinking reagent, such as amelamine resin, an epoxy resin, or a diamine, may be added to react withthe functional groups on the polymer to form a covalent crosslink;second, a polymerizable acid such as acrylic acid or methacrylic acid,may be added to the composition, which can then be subsequently cured;and third, the polymer may be designed to include a pendantcrosslinkable functional group such as a polymerizable ethylenically oracetylenically unsaturated group, a sulfonium group, an epoxy group, or2-oxazoline. An example of a preparation of a polymer that containsethylenic unsaturation is illustrated as follows:

where Nu—═ is a nucleophile (such as a tertiary amine or a sulfide) thatcontains ethylenic unsaturation; and A, Ar, and L are as previouslydefined. In the previous illustration, a polymerizable acid monomer, apolymerizable aryl halide, preferably vinylbenzyl chloride and apolymerizable non-interfering monomer are copolymerized to form apolymer having acid groups and benzyl halide groups. The polymer is thenreacted with a nucleophile that contains ethylenic unsaturation toimpart crosslinking capabilities to the polymer. An example of asuitable nucleophile with ethylenic unsaturation is the followingcompound:

In the case where a polymerizable acid is used as the crosslinkingagent, it is preferred that it be added to the inner salt to form acrosslinkable polymer as shown in the following illustration:

Another example of a polymer that includes a pendant crosslinkable groupis a polymer formed by the copolymerization of 2-isopropenyl-2-oxazolinewith the polymerizable strong cation monomer and the polymerizable acidmonomer.

When the composition that includes a crosslinking agent or acrosslinkable functional group is coated onto a substrate, the coatingis preferably allowed to set before means such as free radicalinitiation or heating or UV radiation is used to promote crosslinking.

It is to be understood that the sol of the present invention can be usedin combination with solutions or latexes containing similar polymers toform useful films and coatings. In addition, the composition may includeproperty enhancing additives such as fillers, pigments, leveling agents,viscosity modifiers, wax dispersions, anti-oxidants, or combinationsthereof.

The compositions of the present invention can be used, for example, tocoat or protect floors, automobile parts, human skin, countertops, wood,furniture, and the interiors or exteriors of houses. The compositionsmay also include additives such as pigments, dyes, fungicides, orbactericides.

The following example is for illustrative purposes only and is notintended to limit the scope of this invention. All percentages are byweight unless otherwise noted.

EXAMPLE 1

Preparation of a 20 Weight Percent Sol

Water (30 g), 1-propanol (30 g), methylmethacrylate (6.3 g), methacrylicacid (0.3 g), butyl acrylate (2.6 g), and M-Quat (2.6 g,2-[(methacryloyloxy)ethyl]trimethylammonium chloride, as a 74% active inwater, obtained from Bimax, Inc.) were added to a 1-L reaction vessel.The mixture was heated with stirring to 80° C. under nitrogen, whereuponfour liquid streams were simultaneously and continuously added to thevessel. The streams were added over a 5-hour period using 100-mLsyringes driven by a Sage Instruments syringe pump Model 355(Cole-Palmer Instrument Company). After the addition was completed, thereaction was maintained at 80° C. for an additional hour. The contentsof the four streams are shown in Table 1.

TABLE 1 Stream No. Component Amount 1 Methyl Methacrylate 56.8 g (0.58mol) Methacrylic Acid 3.1 g (0.036 mol) Butyl Acrylate 23.0 g (0.18 mol)Styrene 10.5 g (0.1 mol) 2 M-Quat 7.5 g (5.6 g active, 0.027 mol) Water75 g 3 VAZO ® 52^(a) 2.00 g 1-Propanol 75 g 4 1-propanol 45 g water 45 g^(a)2,2′-azobis(2,4-dimethylpentane nitrile) obtained from E.I. duPontde Nemours & Co., Inc.

The polymer solution was cooled and percent solids were determined to be24.8 percent using a Labwave 9000 Moisture Solids Analyzer (availablefrom CEM Corp., Matthews, N.C.). The viscosity of the sample was 227cps. A portion of the polymer solution (200 g) was diluted with1-propanol (49.6 g), and water (49.6 g). The diluted solution wasthoroughly mixed, then placed onto a Caframo mixer (available fromFisher Scientific) at 1200 rpms. The sample was diluted further withwater (196.8 g) to provide a solution containing 10 percent solids. Thisdispersion was placed on a rotary evaporator to remove substantially allof the 1-propanol to form a sol containing 25 percent solids, which hada viscosity of 26.6 cps.

What is claimed is:
 1. A method for preparing an aqueous-basedsuspension of a polymer having a backbone that contains pendant cationicgroups and pendant acid groups, which method comprises the steps of: a)forming a solution of a polymer that contains pendant cationic groupsand pendant acid groups in an aqueous-based solvent for the polymer,which aqueous-based solvent contains a first organic solvent; and b)concomitantly adding water and removing a sufficient amount of the firstorganic solvent from the solution to form a composition characterized bybeing reversibly dissolvable and reconstitutable by addition and removalof a second organic solvent.
 2. The method of claim 1 wherein thepolymer further contains structural units formed from the polymerizationof a non-interfering monomer which is an acrylate, a methacrylate, aC₃-C₁₈-perfluoroalkyl acrylate or methacrylate, an alkenyl aromatichydrocarbon, or a C₁-C₄ alkylstyrene, and wherein the ratio of thestructural units formed from the polymerization of the non-interferingmonomer to the sum of the pendant cationic groups and acid groups is notless than 70:30 and not more than 99:1.
 3. The method of claim 2 whereinthe first organic solvent has a boiling point below 100° C.
 4. Themethod of claim 3 wherein the aqueous-based solvent contains methanol,ethanol, 1-propanol, 2-propanol, 2-methyl-2-propanol, or2-methyl-1-propanol, ethyl acetate, or acetonitrile, or a combinationthereof, at a level of not less than 20 weight percent and not more than70 weight percent based on the weight of the water and the first organicsolvent.
 5. The method of claim 4 wherein the pendant cationic groupsinclude quaternary ammonium groups and the pendant acid groups includecarboxylic acid groups, and the ratio of the carboxylic acid groups tothe quaternary ammonium groups is in the range of 0.1 to
 10. 6. Themethod of claim 4 wherein a sufficient amount of the first organicsolvent is removed from the solution to form a sol having a solidscontent of at least 20 percent.
 7. The method of claim 6 wherein thependant cationic groups include structural units formed from thepolymerization of 2-((methacryloyloxy)ethyl)trimethylammonium chloride,the pendant acid groups include structural units formed from thepolymerization of methacrylic acid or acrylic acid or a combinationthereof, and the structural units formed from the polymerization of thenon-interfering groups include methyl methacrylate or butyl acrylate, ora combination thereof, wherein the ratio of the structural units formedfrom the polymerization of the non-interfering groups to the sum of thependant acid groups and pendant cationic groups is not less than about85:15 and not more than 98:2, and wherein the first organic solvent isthe same as the second organic solvent.
 8. The method of claim 3 whichincludes in step (a) the addition of a coalescing agent which is anorganic liquid that is miscible with water in the proportions used andwhich has a boiling point of greater than about 100° C.
 9. The method ofclaim 8 wherein the coalescing agent includes a glycol ether or adibasic ester or a combination thereof at a concentration of not morethan 10 weight based on the weight of the sol and the coalescing agent.10. The method of claim 4 wherein in step (b), at least 95 percent ofthe first organic solvent is removed from the solution.